A. Field of the Invention
The present invention relates to a contact image sensor module (hereinafter referred to as CIS module), especially to a CIS module having spring mountings at both ends thereof. The improved structure of the CIS module can assure a document sheet in focus, thereby to improve the picture quality of images.
B. Description of the Prior Art
The scene depth of a conventional contact image sensor is only about 0.3 mm. Any manufacture error or structure distortion will easily shift the document sheet away from the focus. To keep the document sheet staying within such short scene depth, the conventional carriage 2 contains an internal spring 4 at the bottom of the carriage as shown in FIG. 1. The function of the internal spring 4 is to lift the contact image sensor module 1 up to contact the bottom surface side of the sheet table 6. Refer to FIG. 1, a contact image sensor module 1 is loaded in a fitting carriage 2. When the carriage 2 is supported by a guiding device 3, the CIS module 1 can contact tightly with the bottom surface side of the sheet table 6 with sliding blocks 5a, 5b interposed therebetween while being driven by the guiding device 3. With the spring 4, the CIS module 1 can contact tightly with the bottom surface side of the sheet table 6 to keep the document sheet in focus even if the housing is distorted. However, for the concern of convenience in assembly, the conventional structure as illustrated in FIG. 1 still has a few drawbacks. For instance, the spring 4 must be located precisely and firmly at the bottom center of the carriage 2. In addition, the guiding device 3 must be carefully installed to keep the carriage 2 in balance. It would be desirable to simplify the structure of the conventional CIS module and make the assembly easier.